A while ago, "Scaper1" posted about losing a lot of fluid out of the balloons of the Poiesis Duette Catheters, 10cc and 5cc ports. I decided to experiment with a used catheter and compare 7 days of balloon inflation.
I filled the "non black" (orange in my case-16Fr) port with 10cc of sterile water and the "black" port with 5cc of sterile water, per the instructions for balloon inflation. I placed the catheter on a paper towel which I had labeled with the day of inflation. I took a picture of the inflated balloons. I waited 7 days and took another picture of the same catheter.
Yes the balloons did lose fluid by a significant amount as you can see in the picture. The fully inflated balloons are clear and stretched out. The balloons, 7 days later are not at clear and visibly smaller. The pictures are taken from the same distance away, or very close to the same distance. I placed the catheter on a paper towel to absorb any liquid. The paper towel was never visibly or to the touch wet. What's more, there was no water mark on the paper towel as there would be if it had been wet and then dried. I presume the fluid slowly evaporated through the silicone membrane of the balloon. After taking the photos, I deflated the balloons. There were a little more than 2cc left in the black port balloon and 7cc left in the non black port balloon. Whether this is the same amount of liquid that would be lost if the catheter was inside the bladder is hard to say.
Seems like it would be good practice to check the balloons about every 10 days by withdrawing liquid from the balloons and refilling them. I think I would test the black port (cushioning balloon) first. If the balloon had lost 1cc (20%), I think I would just re-inflate the 5cc balloon with 5cc of sterile water, and stop, then possibly repeat the inflation test in a few days. If I found the 5cc balloon had lost more than 20%, I would re-inflate it with 5cc of sterile water and then test the 10cc balloon for water loss.
I will send my results to Poiesis for their take on this water loss.